Planographic printing plate



Get 6, 56 G. HALPERN ET AL 2,766,688

PLANOGRAPHIC PRINTING PLATE Filed Feb. 24, 1955 INVE gkEGO-QY awn? BY WTORS PLANOGRAPHIC PRINTING PLATE Gregory Halpern and Robert Gumbinner,Tarrytown, N. Y., assignors to Polychrome Corporation, Yonkers, N. Y., acorporation of New York Application February 24, 1955, Serial No.490,268

20 Claims. (Cl. 101-1492) Our present invention is acontinuation-in-part of copending applications Serial No. 214,176, filedMarch 6, 1951, Halpern application Serial No. 378,136, filed September2, 1953, Halpern application Serial No. 378,135, filed September 2,1953, and Gumbinner application Serial No. 378,137, filed September 2,1953, and relates to an improvement in planographic printing, andparticularly to a novel plate or sheet having a water impervious coatingand a hydrophilic coating bonded to each other in a novel manner and bynovel means.

The art of planographic printing depends, as does the older lithographicart, upon the immiscibility of oil and water and upon the preferentialretention of a greasy image-forming substance by the image areas, and asimilar retention of an aqueous dampening fluid by the nonimage areas.

In the preparation of planographic printing plate surfaces, it was atfirst customary to employ metal plates as substitutes for the printingstone originally used. The surfaces of these metal plates were grainedby an expensive marble operation which rendered the surfaces capable ofretaining films of water and becoming thereby grease-repellent.

In addition to its cost in time, labor and equipment, the grainingoperation is objectionable due to the fact that plates prepared by itmust be subjected to etching, gumming and other operations both duringthe preparation and operation of the plate. Furthermore, satisfactorygrained metal lithographic surfaces can be prepared on only a fewrelatively expensive metals.

In order to eliminate the necessity for the expensive grainingoperations, and the use of expensive bases, various hydrophilic coatingsin combination with metal or non-metal supports were developed. However,these nonmetallic base planographic printing plates have considerablelimitations with regard to durability, curling tendency, stretching,cohesive strength, and the number of satisfactory copies obtainable.

Accordingly an object of the present invention is to provide aplanographic plate or sheet which is durable, does not curl or stretch,avoids graining, is of the necessary strength to withstand the variousprinting operations, and which permits a desirable number of copies tobe produced.

Another object of our invention is the provision of a novel starch-typeprinting element which will give truer reproduction, result in a longerrunning plate, and provide a good base for a presensitized plate.

A further object of the present invention is the provision of a novelplanographic printing plate or sheet having a strong wear resistantbase, a water impervious coating which does not decrease substantiallythe original flexibility of the base and a novel hydrophilic coatingreceptive to grease or water and repellent to either grease or waterwhen the other is applied first.

Further objects will be apparent from a consideration of the followingdescription and the accompanying draw ings wherein- Figure 1 is anenlarged fragmentary cross-section of a planographic printing plate orsheet of the invention.

Figure 2 is an enlarged fragmentary cross-section of anotherplanographic printing plate or sheet.

Figure 3 is an enlarged fragmentary cross-sectional view of anotherplanographic sheet showing the modification of the invention.

Figure 4 is an enlarged fragmentary view of a further planographic sheetshowing another modification of the invention.

Figure 5 is an enlarged fragmentary view of another planographic sheetshowing still another modification of the invention which employs alight sensitive coating.

Figure 6 is an enlarged cross-sectional view of a simplified short-runplate made in accordance with another modification of our invention.

Referring first to Figure 1, we have here shown a cross-sectional viewof our novel planographic printing sheet in which the base 10 ispreferably a wet strength kraft type paper or other appropriatecellulose stock having a formation which is uniform and may be impressedor calendered to have a fine surface.

Necessary and inherent characteristics of the paper material which willform the base 10 will be described after a general description of ourplanographic printing sheet of Figure 1.

The paper or other flexible base 10 is coated on both sides with waterimpervious coatings 12, 22 preferably a ureaformaldehyde material, soapplied that it will be bonded to the paper base by impregnation of aportion thereof to the extent of approximately .001" below the surfaceas shown at 12a and 22a and extending above the original surface of thepaper base on both sides totaling an amount of the order of .001", asshown at 12 and 22.

A hydrophilic layer 14 containing starch carbamate is coated on thewater impervious coating or surface 22.

A nitrocellulose layer 15 is coated on impervious layer 12 to reducecurling tendencies. However, it is also possible to utilize any othersuitable anti-curling backing.

In the making of a planographic printing sheet in accordance with ourinvention, we have found that several necessary and inherentcharacteristics must be present in each of the components; base layer10, water impervious coatings 12 and 22, the hydrophilic layer 14 andlayer 15. In the following we shall describe our invention in connectionwith a flexible paper base.

Paper base 10 In accordance with the present invention various bases maybe used for planographic printing plates as metal, cloth, plastic,cellulose acetate or paper for base 10.

It is essential that base 10, where a paper is used, be of relativelylong fibres, such as kraft, having a thickness of .003 to .010 inchesdepending upon the printing press on which it is to be used. The mostsuitable thickness is between .004 and .008 inch, the thicker paperbeing used to provide for longevity of use and the thinner paper forshort runs.

One of the main considerations in selecting the stock is the amount ofwear and tear on the plate due to the pressures of the blankets, the inkrolls and the water fountain roll. The base paper is hung on eitherhooks or pegs. These give rise to various tensile stresses which cancause distortion. This, coupled with the additional fact thatlithographic offset printing usually calls for long runs, requires theuse of strong bases.

Paper itself initially has poor resistance to moisture. The moisturestretches, wrinkles and reduces the tensile strength of the paper.

Wet strength paper is a paper which is treated chemically or in any wayso as to reduce the deleterious effects of water upon the paper.

We have discovered that paper treated with a 22 /2% by weight melamineformaldehyde resin based on the weight of fiber in the paper mill willprovide desired wet strength for planograph printing reducing theseeffects of moisture. The melamine formaldehyde resin is applied as apart of the paper manufacturing process.

Due to the mechanical stresses exerted by the prongs and hooks, the rawstock should be of such a nature as to have a good fibre distribution inboth directions with and against the grain.

Preferably, the paper should be made on a Fourdrinier with an equalstrength or close to an equal strength in both directions.

The raw stock should be resistant to brittleness caused upon theapplication of heat, etching or chemicals. A pure cellulose paper, of acellulose sulphate stock, would be preferred for base 10. The formationshould be of uniform type and preferably compressed so as to have a veryfine surface.

The paper as thus formed in accordance with the above has substantiallyno imperfections or non-uniformities on the surface or the interior andis calendered as hereinafter described to give it the desirable gloss ortexture and density to keep it from being too spongy.

Waterproof layers urerzformaldehyde 12, 22

The wet strength paper base it) formed in accordance with the abovedescribed procedure is next coated with the water impervious layers 12and 22. This waterproof composition may be ureaforrnaldehyde solution oremulsion or one of the following: melamine formaldehyde resin,nitrocellulose, neoprene, nylon, phenolformaldehyde resin, vinyl, alkyd,polyester or rubber hydrochloride resins.

The specific ureaformaldehyde is a 65% solid dispersion of a lowmolecular weight ureaformaldehyde in water. This material polymerizesafter being applied to the paper by the action of heat and the loss ofwater. The ureaformaldehyde coating is calendered to a uniform caliperand desired finish depending on the caliper and finish of the originalstock.

In addition, further curing or polymerization and flowing of theureaformaldehyde occurs at the calender when heat is applied to therolls. The paper is contacted with hot calender rolls from 3 to 10seconds at 170 F.

Ureaformaldehyde coated paper is aged for two to seven days in order topermit stabilization of setting so that top coats will not curl the basepaper when applied and also so that ureaformaldehyde will not dissolvein the top coat solution. If cured for too long a period, the top coatswill not bond. In fact, in order to provide a more effective bond withthe top coat, it is often desirable to use a second ureaformaldehydeprime coat. The hydrophilic starch carbamate coating is then applied tothis second prime within 48 hours. This embodiment is set forth in moredetail in Halpern patent application Serial No. 378,136, hereinbeforereferred to.

Ureaformaldehyde in a thin film is more flexible than a thick film. Thesurface must be coated with ureaformaldehyde in addition to theureaformaldehyde absorbed inasmuch as the paper would be still affectedby moisture without the surface coat, as in Figure 2. Thus, too littleureaformaldehyde results in a paper affected by moisture, Figure 2, andtoo much ureaformaldehyde results in a paper that is too brittle. Itshould be noted, however, that the ureaformaldehyde may be dispensedwith in the plate of Figure 6, hereinafter referred to in more detail,in which the hydrophilic coating contains a large amount ofmelamineformaldehyde.

The preferred ureaformaldehyde may be combined with a catalyst to hastenthe polymerization of the ureaformaldehyde. As described, theureaformaldehyde penetrates the base 10 at 22c and 12a to a depth ofabout .001" on each side of the paper base 10 and extends above thesurface of base 10 to a thickness of about .0005," as

at 12 and 22 so that thickness of the paper base is increased by about.001". The weight is then approximately 1 to 7 of dry ureaformaldehydeto paper.

The extent of saturation by the coating which in turn determines thebrittleness of the base is controlled by the absorbency of the rawstock; the viscosity of the solution; and by the time the coating takesto set. Material that will bend around at least a mandrel 4:", on whichit is turned, without cracking, has the desired flexibility.

Hydrophilic layer 14 To the paper base 10 thus formed and made waterimpervious by coating layers 12, 22, 12a and 22a, the hydrophiliccoating 14 is now applied as hereinafter described. The hydrophiliclayer 14 is a composition of a starch carbamate, fillers, a hardener,water and a wetting agent, being .0003 to .0005 inch thick. One or amultiplicity of coating may be used.

We have discovered that a marked improvement in grease and waterselectivity is secured by the use of starch carbamate. The use of starchcarbamate in the hydrophilic layer has been found to be particularlyadvantageous. For one thing, the starch carbamate gives much betterbalance; that is, it is highly grease receptive when,

dry and grease repellent when wet, thereby providing an improved balancebetween the hydrophilic and hydrophobic properties. Moreover, it isreadily hardened to make it water receptive, gives much truerreproductions LIL.

To the starch carbamate is added a filler consisting of clays and/ orpigments. The fillers fulfill specific purposes, giving porosity,absorbency and imbibition and thus acting as a trap for the greasy inkas well as assisting in the necessary absorption of wetting fluid fromthe Water fountain roll.

An example of medium oil absorption filler is titanium dioxide which isadded 25 parts to 10 parts of starch carbamate by weight. 'Anotherfiller is china clay which can be used parts to 10 parts of starch.Still another filler is a combinaiton of titanium dioxide and china claywhich can be used 25 parts of titanium dioxide and 30 parts of chinaclay to 20 parts of starch. The titanium dioxide or antimony oxidehardens, adding to grease receptivity. The hardening of the titaniumdioxide, however, makes corrections ditficult. China clay, on the otherhand, softens the coating and makes erasures easy. Blancfixe, silica,bentonite or carbon black may be used as substitutes for the china clay.

Incorporating some carbon black 2% solution will allow acceleratedcuring at lower temperature using a system of infra-red bulbs as thecarbon black absorbs the heat.

The water added to the solution is a distilled or d,6-

ionized water to assure a given pH value of the emulsion and freedomfrom unwanted impurities.

There is added to the above solution another solution consisting of 1 /2parts of oxalic acid, parts of glyoxal, 10 parts of water, basingeverything on 10 parts of starch carbamate. A small amount of adetergent such as Tergitol 7 is also added to insure spreading of thecoatrngs.

A typical formulation is as follows:

The hydrophilic layers 16 and 17 consist of the following mixture in theproportions indicated:

30 lbs. dry starch carbamate 600 lbs. water 3 lbs. ozs. titanium dioxide4 lbs. 11 /2 ozs. china clay To this is added, just before using, thefollowing mixture in the proportions indicated:

107 gm. oxalic acid 2520 cc. water 35.4 gm. Parez resin 611 (melamineformaldehyde) 71 cc. Tergitol (sodium alkyl sulfate surface) activeagent The starch carbamate serves as the hydrophilic material.Utilization of the carbamate derivative allows for a greater greasereceptiveness than using starch per se, and a marked improvement ingrease and Water selectivity is secured.

The inclusion of the Parez No. 611 melamine-formaldehyde resin in thestarch carbamate layer produces a particularly desirable plate as themelamine resin assures that the plate will remain water-receptive whenhardened.

The starch carbamate coated papers as described above store well, havegood hydrophilic qualities, hold moisture on the press, are easilycleaned, have high cohesive strength and yield a large number of goodcopies.

Backing layer 15 The plates may be coated at 15 on the back 12 toprevent curling. One of the reasons for curling is the fact that oneside may, by the nature of the coating process or because ofunforeseeable causes, have a slightly thicker coating than the otherside and when the coating contracts, the plate warps. Starch tends tocurl papers less than other hydrophilic coatings, as for example,polyvinyl alcohol. A starch carbamate therefore is also useful as theback coating 15 to stiffen the base slightly and prevent curling.

Modifications In one embodiment of the present invention we prefer toutilize two thin coats 16 and 17 as illustrated in Figure 3 inpreference to one thick coat.

Utilizing two thin coats 16 and 17 helps to cover flaws, gives moreuniform drying throughout the final thickness, and provides better depthof printing surface. The first coat 17 is primarily a bonding coatingand not necessarily a printing coat.

In bonding to this partially cured ureaformaldehyde 22, the coat 17hardens somewhat and it is only in the second coat 16 that completecontrol is achieved as the urea-formaldehyde 22 is by this time cured.

The second coat 16 may differ from the first coat 17 in an additionalmanner by having the filler proportioned differently. For example,titanium dioxide 15 parts, osmo-kaolin 18 parts. Although the originalcomposition of the two coats may be the same, the application of thesecond coat 16 allows some of the colloid and water to seep into thefirst coat 17 essentially changing the composition of the second coat16.

Where the plate on which the information to be printed is recorded by atypewriter, the base must be a thin supple paper to provide thenecessary flexing required of typewriter paper. There are manyapplications where several plates are put in a pack, all to be at leastin part typed up together through the used carbon. For example, theyhave common information and also in dividual information. The finalsheet will then have information from several different lithographicplates. In order to have good transfer of copy through a system pack,the plate must be thin and supple and transfer the character of thetype. Hence the paper would be as thin as possible, i. e., .004 inch oreven thinner, and at the same time have the strength necessary foroffset printing.

There are applications wherein a single plate is typed, as for example,letters, advertising, etc. The plate would then be more rugged.

The multiple stock, as above, should have a weight of approximately 60pounds of 24" x 36"500 and the single plate direct image stock, asabove, should be between 70 and pounds for the same dimensioned paper.

Figure 4 illustrates an embodiment wherein two hydrophilic coatings areused as referred to in Halpern copending application Serial No. 378,135,filed Septembr 2, 1953. A first hydrophilic coating 24 is coated on theplate 20 on the side away from the tendency to curl; in this case, oncoating 22. The coating 24 is a polyvinyl alcohol coating having thefollowing composition:

Polyvinyl alcohol 35 pounds. Water 600 pounds. Titanium dioxide 4pounds1 ounce. China clay 5 pounds.

Oxalic acid 50 grams.

Polyvinyl alcohol coatings bind satisfactorily to the flexible ureaformaldehyde coating 22 as described above.

A second hydrophilic coating 25 is coated over the coating 24. Thecoating 25 is of essentially a starch carbamate composition and similarto the coatings 14, 16 and 17 of the planographic printing platesdescribed above in reference to Figures 1 to 3.

The formulation of the hydrophilic layer 24 consists of dry starchcarbamate 30 pounds, water 600 pounds, titanium dioxide 3 pounds 15ounces, china clay 4 pounds 11 /2 ounces, to which is added just beforeusing oxalic acid 107 gm., water 2520 cc., Parez resin 607 35.4 gm. andTergitol 71 cc.

Figure 5 illustrates a plate where the hydrophilic layer 30 is the basefor a photographic coating of the type referred to in Gumbinnercopending application Serial No. 378,137, filed September 2, 1953. Herethe paper base 10 is covered with first prime coats 12 and 22 which inturn may be covered with second prime coats, applied to both sides ofthe plates, 28 and 29. These coats have fillers in them. The first primecoat has walnut shell flour, in addition to the ureaformaldehyde. In thesecond prime coat, we add an amount of titanium dioxide approximately50% of the ureaformaldehyde. The hydrophilic layer 30 is then placed onsecond prime coat 28 and serves as a suitable base for the applicationof lightsensitive compound.

There are two types of photographic plates; the presensitized plate andthe customers sensitized plate. The customers sensitized plate utilizesan application of sensitizing material on the plate before exposing thenegative. The presensitized plates, however, are exposed directlythrough the negative without any previous treatment. The customerssensitized plate solution applied is ammonium dichromate and eggalbumen, prepared from an egg albumen solution of approximately a 9percent solution of egg albumen in water and ammonium dichromate ofapproximately a 25 percent solution in water, the ratio of egg albumento ammonium dichromate being approximately 3 to 1 by Weight in the finalsensitizing solution.

In the pre-sensitized plate, the application of a coating of a lightsensitive diazo compound 31 to the surface of the hydrophilic layer 30has been found to be particularly advantageous. Instead of having alaminated plate in which the light sensitive material is in the form ofa film 7 which has been glued to the surface, the diazo liquid may besimply applied to the surface of the plate.

When films were applied as in the prior art, the expansion andcontraction of the paper was always found to be different from that ofthe film and, therefore, there was a tendency for the film to separatefrom this paper base.

The diazo compound applied as the light sensitive surface provides anincreased sharpness in the character of the half-tones due to the closercontact which the chemical has with the paper than can be obtained by afilm through which the light must pass.

In the preferred form of my invention this light sensitive material is aformaldehyde condensation product of diazo diphenylamine sulphate. Thisis applied as a coating of the following solution:

100 parts of water 2 parts of this diazo .65 part of zinc chloride partof wetting agent (10% solution Saponin) This compound is sprayed on to apair of squeeze rolls made of rubber about 4" in diameter between whichthe plate is passed.

The resulting coating is of micron depth, less than one ten-thousandthof an inch and results in a reduction of the light fraction.

Accordingly, there is less tendency for the light rays to angle off asoccurs where laminated coatings are employed. Because of the thinness ofthe light sensitive coating, the negative is so close to the base thatlight does not have a chance to spread. This results in an image offiner composition and increased sensitivity. Moreover, with the novelcoating as here described, a single application of the chemicalsdesensitizes the non-printing areas making the image highly inkreceptive and visible.

After the present plates have been exposed, it is free from light orgrease susceptibility. This builds up a high grease-receptive coatingwhich makes the image visible on the plate.

More specifically, the diazo may be the condensation product ofparaformaldehyde and paradiazodiphenylamine (4 parts of formaldehyde to30 parts of paradiazodiphenylamine by weight).

Referring now to Figure 6, it can be seen that a simple short run platemay be made in which the starch carbamate-melamine formaldehyde, coating17, hereinbefore referred to, is applied directly to a wet strength orsurface treated sizing paper. In this modification, however, it isnecessary to employ a considerably larger quantity of the Pare-z No. 611melamine formaldehyde resin. Thus, in the formulation referred topreviously, the amount of melamine formaldehyde would be increased 10-40times to about 350l500 gms., or to about 2 to percent of of the weightof dry starch carbamate. In this modifica tion, one or both sides may becoated with the starch carbamate-melamine-formaldehyde layer, asdesired. If only one side is coated, it would be advisable to coat theopposite side with an anticurl compound.

Methods of manufacture Our invention is capable of embodiment in manydifferent forms of processes for producing the above described plates,and we shall choose, for the purpose of H ture of ureaformaldehyde withflour, which may be walnut shell flour8% by weight. The dry material ismixed with water in approximately the proportion of 40% ureaformaldehydedry to water by weight. To that may In actual practice we have foundthat the catalyst acts immediately to cause a thickening and change ofthe viscosity of the ureaformaldehyde. This thickening occurs before thecoating has been applied and is un-' desirable. The viscosity of theureaformaldehyde alone is 13 seconds at 27 C. with a 150 gram load usinga Stormer viscosimeter. In order to predetermine the viscosity of themixture ideally, each drop of ureaformaldehyde would be mixedimmediately preceding its ap plication to the paper. Mixing theureaformaldehyde with the catalyst, for example, two hours prior toapplication causes the viscosity to double in this time. An additionalproblem is presented by the fact that some of the solution remains inthe coating machine when the new batch is added. Accordingly we proposeto effect a continuous mixing just before the coating.

In the coating process, the ureaformaldehyde penetrates to about .001inch on each side of the paper and the remainder remains on the surfaceto a height of about .0005 inch.

The paper is then squeezed, polished and dried between about C. and 0,thereby partially curing the resin.

When the resin is in the partially polymerized state, the paper iscalendered and brought to the desired finish. The calendering smoothsout ridges in the partially cured paper by melting and plasticizing theresin, forcing it into the paper and resulting in a solid sheet ofureaformaldehyde without grain.

The waterproofed paper may then be aged if desired, after which thehydrophilic coating is applied. The hydrophilic coating comprises astarch carbamate, prefer-. ably glucosan 2-monocarbamate, distilledwater, fillers, a

hardener, and a wetting agent.

The hydrophilic coating is supplied either in solution The dry powder ismixed in" After the grinding in the mill there is added to thesolutionanother solution consisting of 1 parts of oxalic acid, 10 parts ofglyoxal, 8 parts of monoethyl ether of ethylene glycol, 10 parts ofwater, basing everything on ,7

10 parts of starch carbamate.

The above is prepared as follows: water is heated to F. and oxalic acidis added and dissolved. This warm solution is added to the main coldground solution.

Following this, the monoethyl ether of ethylene glycol and glyoxal areadded to the body of the solution.

The glyoxal is a tanning or hardening agent which tans the colloid. Theoxalic acid also functions as a mild. hardening agent for the colloidand furnishes a source of l acidity which is necessary for thenon-emulsification of inks.

The ureaformaldehyde is mixed for.

The filler is dispersed in the starch The colloid mill utilizes theshearing action' The monoethyl ether of ethylene glycol helps spread thecoating and assists in the smooth setting during the last stages ofdrying and curing.

If the plates are treated to have photographic coats, further coatingoperations are necessary. There are two types of photographic plates;the pro-sensitized plate and the customers senistized plate. Thecustomers sensitized plate solution applied is ammonium dichromate andegg albumen; the egg albumen solution is approximately a 9% solution ofegg albumen and water and the ammonium dichromate is approximately a 25%solution; these are mixed into a single solution with the ratio of eggalbumen to ammonium dichromate being approximately 3 to l by weight. Thecustomers sensitizing solution is applied to the plate by means ofabsorbent cotton swab which achieves an even coating. The plate is thendried utilizing a blower or fan and subsequently exposed to a source ofhigh intensity light in combination with the negative. The source oflight may be carbon arc lamp, sun lamp, photoflood, or any other meanswhich applies ultra-violet radiation.

The plate is held in contact with the negative by means of a vacuumframe or a pressure contact frame. After exposure, the plate is rubbedwith a grease-receptive ink, usually of an asphaltum base. It is thenplaced under running Water and washed until the unexposed egg albumenand developing ink are washed off leaving the hardened sections of theplate which correspond to the light struck areas which were patterned bythe negative. The plate is then gummed and is ready for the press.

The pre-sensitized plate is a plate exposed in a similar manner as thecustomers plate but needs no sensitizing step. After exposure, thepre-sensitized plate is wiped down with a solution of either plain wateror gum solution and then is ready for the press. It is thus much faster.

In the foregoing, we have described our invention only in connectionwith preferred embodiments thereof. Many variations and modifications ofthe principles of our invention Within the scope of the descriptionherein are obvious. Accordingly, we prefer to be bound not by thespecific disclosure herein, but only by the appending claims.

We claim:

1. A planographic printing plate comprising a base of wet strengthpaper, a waterproof resinous coating on said paper and a hydrophiliclayenon the said waterproof coating, said hydrophilic layer comprisingstarch carbamate.

2. A planographic printing plate comprising a base of wet strength papercontaining a melamine formaldehyde resin, said base being of the orderof .004 inch to .01 inch; a waterproof coating on each side, saidwaterproof coating being of the order of .0005 to .001 inch thick andimpregnating the said paper base; a hydrophilic coating containingstarch carbamate on one side of said waterproof coatings and a coatingof curl resisting material on the other side of said waterproofcoatings.

3. A presensitized planographic printing plate comprising a base of wetstrength paper; a waterproof resinous coating on said paper, ahydrophilic layer on the said waterproof coating, said hydrophilic layercomprising starch carbamate and having superimposed thereon an organiclight-sensitive material which becomes waterinsoluble and ink-receptiveupon exposure to light.

4. A presensitized planographic printing plate comprising a waterproofpaper base, a hydrophilic coating on said base containing starchcarbamate and, having a surface comprising a film of light sensitivediazo compound.

5. A presensitized planographic printing plate comprising a waterproofpaper base, a hydrophilic coating on said base containing starchcarbamate therein, and a surface comprising a film of formaldehydecondensation product of diazo diphenylamine sulphate.

6. A presensitized planographic printing plate comprising a waterproofpaper base, a hydrophilic coating containing starch carbamate thereon,and a surface coating comprising a film of light-sensitive diazocompound.

7. A planographic printing plate comprising a base of wet strengthpaper, a Waterproof resinous coating on said paper and a hydrophiliclayer on said Waterproof coating, said hydrophilic layer comprising amixture of starch carbamate and melamine formaldehyde resin.

8. A planographic printing plate comprising a base of wet strength papercontaining a melamine formaldehyde resin, said base being of the orderof .004 inch to .01 inch; a Waterproof coating on each side, saidwaterproof coating being of the order of .0005 to .001 inch thick andimpregnating the said paper base; a hydrophilic coating containing amixture of starch carbamate and melamine formaldehyde on one side ofsaid waterproof coatings and a coating of curl resisting material on theother side of said waterproof coatings.

9. A planographic printing plate comprising a base of wet strength papercontaining a melamine formaldehyde resin, said base being of the orderof .004 to .01 inch; a waterproof coating on each side, said Waterproofcoating being of the order of .0005 to .001 inch thick and impregnatingthe said paper base; a hydrophilic coating containing starch carbamateon one side of said waterproof coatings and a coating of curl resistingmaterial on the other side of said waterproof coatings.

10. A printing plate having a water impervious paper base and aplurality of hydrophilic layers superimposed on each other and mountedon said base, said hydrophilic layers comprising starch carbamate andtitanium dioxide.

11. A planographic printing plate comprising a base of wet strengthpaper, a waterproof resinous coating on said paper and a, hydrophiliclayer on the said coating, said hydrophilic layer comprising starchcarbamate, melamine formaldehyde resin and a filler.

12. A planographic printing plate consisting of a wet strength paper anda hydrophilic layer on said paper comprising starch carbamate andmelamine formaldehyde resin.

13. A planographic printing plate consisting of a Wet strength papercoated with a hydrophilic layer comprising starch carbamate and melamineformaldehyde, the proportion of said melamine formaldehyde to starchcarbamate being between 2 to 15 percent by weight.

14. A printing plate comprising a dense, flexible base and a coating onsaid base containing starch carbamate and a filler.

15. A printing plate comprising a paper base and a gtlilating on saidbase containing starch carbamate and a 16. A planographic printing platecomprising a water impervious paper base and a hydrophilic layer mountedthereon, said hydrophilic layer containing starch carbamate.

17. A presensitized planographic printing plate comprising a dense,flexible base, a coating on said base containing starch carbamate andsuperimposed upon the said coating an organic light-sensitive materialwhich becomes water-insoluble and ink-receptive upon exposure to light.

18. A planographic printing plate comprising a dense, flexible base anda hydrophilic layer on said base containing starch carbamate andmelamine formaldehyde resin.

19. A planographic printing plate comprising a paper base and aplurality of hydrophilic layers on said base and superimposed on eachother, each of said layers containing starch carbamate.

20. A planographic printing plate comprising a paper base treated withmelamine-formaldehyde resin, a Waterproof coating on said base, a firsthydrophilic coating on said waterproof coating and a second hydrophiliccoating superimposed on said first hydrophilic coating, said firsthydrophilic coating being of a polyvinyl alcohol composition having goodbonding to said waterproof coating and 11 to said second hydrophiliccoating, said second hydrophilic coating being a starch carbamatecompcsition.

References Cited in the file of this patent UNITED STATES PATENTS2,309,027 Toland et a1 Jan. 19, 1943 2,313,848 Toland et a1 Mar. 16,1943 2,327,380 Toland et a1 Aug. 27, 1943 7 12 7 Van Epps May 9, 1944Siifkin June 28, 1949 Worthen Dec. 19, 1950 Gaver et a1 Ian. 23, 1951Wolff Aug. 7, 1951 Wood Mar. 18, 1952 Neugebauer et a1 Aug. 18, 1953

14. A PRINTING PLATE COMPRISING A DENSE, FLEXIBLE BASE AND A COATING ONSAID BASE CONTAINING STARCH CARBAMATE AND A FILLER.
 17. A PRESENSITIZEDPLANOGRAPHIC PRINTING PLATE COMPRISING A DENSE, FLEXIBLE BASE, A COATINGON SAID BASE CONTAINING STARCH CARBAMATE AND SUPERIMPOSED UPON THE SAIDCOATING AN ORGANIC LIGHT-SENSITIVE MATERIAL WHICH BECOMESWATER-INSOLUBLE AND INK-RECEPTIVE UPON EXPOSURE TO LIGHT.